Wireless communication devices need to control the power at which uplink transmissions take place to reduce the potential for interference and to save battery power. Often the power necessary for uplink transmission depends on propagation distances. In addition to propagation distances, the frequency of transmission, channel interference, and the propagation environment make important contributions to the power necessary for successful and reliable uplink transmission.
Various wireless standards, including The Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) specifications, employ both closed loop and open loop mechanisms to address power control. In a closed loop mechanism, an evolved Node B (eNodeB) directly controls uplink transmission power by communicating explicit power control commands to a wireless communication device/user equipment (UE). In open loop mechanisms, a determination of uplink transmission power relies, at least in part, on estimates derived from measurements of downlink transmission path-loss.
Open and closed loop mechanisms for power control are being employed in environments of ever increasing numbers of UEs with ever increasing abilities. These abilities, such as the ability to display audiovisual presentations and to transmit and receive pictures, information related to games, television, movies, and so forth, increase the need both for greater bandwidth, in terms of greater frequency ranges within which wireless communication can take place, and for more efficient use of that bandwidth.
To accommodate these needs, wireless communication standards are coming to rely on technologies such as carrier aggregation, to increase bandwidth, and technologies related to multiple input, multiple output (MIMO) and heterogeneous networks to improve the efficiency with which that bandwidth is used. These technologies, however, complicate approaches to power control that rely on timing advances and open loop mechanisms.
Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended.